#  Jenni Austiff Thesis Defense (James Hanken, Advisor) 

 



####  calendar\_today Date and Time 

 **May 19, 2023** 

 09:00AM - 09:00AM EDT 

####  pin\_drop Location 

 **Biological Laboratories Lecture Hall 1080, 16 Divinity Avenue**  



 

 



 

 **Title:** Development and evolution of the larval stomach of the Budgett’s Frog, *Lepidobatrachus laevis*

 **Abstract:** Anurans have a strongly conserved biphasic life history with extremely morphologically- and ecologically- divergent tadpole and adult phases. Tadpoles are typically aquatic, filter-feeding herbivores that transform dramatically during metamorphosis into semi-terrestrial, bulk-feeding carnivores. The gut morphology of these life phases is very constrained–tadpoles have a reduced, highly derived stomach while adult frogs have a more typical vertebrate gut with a large digestive stomach. *Lepidobatrachus laevis* tadpoles have evolved extreme larval carnivory, even cannibalism, with nearly complete ecomorphological overlap with adult frogs. Their stomachs develop peramorphically and are adult-like at hatching. This dissertation investigates the extent of the heterochronic shift and developmental mechanisms generating the adult-like tadpole stomach morphology in *L. laevis*.

 In Chapter 1, using histological examinations of microanatomy, I find that the developmental trajectory of the stomach of *L. laevis* is highly derived from the plesiomorphic state, and the development of an adult stomach morphology is completely peramorphically shifted into larval development. The stomach of *L. laevis* does not remodel at metamorphosis. In Chapter 2, I use RNA-seq to investigate the genetic mechanisms by which development of the adult-like stomach occurs, with particular focus on the role of decreased retinoic acid in mediating this developmental shift. The findings in this chapter show that modules of stomach development in *L. laevis*, including those regulated by retinoic acid, are temporally shifted to resemble stomach metamorphosis in *Xenopus tropicalis*. The evidence presented in these two chapters shows that a complete heterochronic shift has occurred in the development of *L. laevis* tadpole stomach morphology.

 **Committee:** James Hanken (Advisor), Elena Kramer, Mansi Srivastava, Cliff Tabin (HMS)



 

 



 

 See also:- [ OEB Thesis Seminar ](/event-type/oeb-thesis-seminar)
 
 

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